Research On Flexibility Investment In Manufacturing System With Setup Times

Flexibility is the ability that manufacturing system produces different kinds of parts or products by adjusting production resources to cope with changes in the external and internal environment. With the diversification of customer demand and the increasing complexity of the production environment, more and more enterprises invest in manufacturing flexibility to obtain and maintain competitive advantage in the rapidly changing environment. Thus, measure flexibility benefits and choose an optimal flexibility structure to guide managers'flexibility investment decisions have an important significance, both theoretically and practically. Based on analyzing and summarizing researches on flexibility measurement and flexibility investment,considering the existence of setup times, this paper mainly investigates the investment issues of total flexibility structure and chaining structure by the analytical method, and further proposes a multi-objective decision-making methods to analysis the flexibility investment in manufacturing systems with arbitrary structure. The results can be used to guide the manufacturing flexibility investment and improvement. The work and contribution in this research can be divided into two parts as follows.Firstly, the value of total flexibility and chaining structure flexibility is measured analytically. Based on the shift rule of the production resources in flexible manufacturing system, this paper valuates flexibility through the incremental output in flexible system compared with the rigid system, as well as analysis flexible investment feasibility. The impacts of flexibility factors (demand fluctuations, setup times and chain length) on flexibility are further investigated. It is found that flexibility benefits are related to the external environment and production environment, which will increase with the magnitude in demand fluctuation and decrease in setup time. For given demand distribution and setup times, the optimal length (i.e. the number of products or plants) of a 2-SC configuration which brings the maximal increased expected sales is determined. Considering setup times, it is better to invest multiple short chains than a single long chain in the manufacturing system. It's better to invest for a configuration with multiple short chains, each with the optimal length, other than a single chaining configuration.Secondly, a multi-objective decision-making method on flexibility investment for non-homogeneous manufacturing system is proposed. A two-phase flexibility investment model with flexibility measured by the profit index and efficient index is developed. In the first phase, under any given flexibility structure, a production decision model is established. In the second phase, we will choose the best flexibility structure to invest by comparing the expected performance obtained from the first stage. Considering the complexity of the model solution, a multi-objective flexible design rule is proposed to help managers determine flexible investment structure conveniently. The numerical analysis shows that the flexible structure under the flexible design rule can obtain equivalent flexibility benefits as total flexibility but only need a cost less than or similar to the 2-SC structure.This study aims to provide some guidelines to make flexibility investment decisions, also present an idea to the researches on manufacture flexibility measurement and investment.